The Royal Geographical Society has unveiled evidence that the devastated region around the Aral Sea in Central Asia is the world's worst ecological disaster.

Three British scientists have just come back from a visit to the lake that straddles the former Soviet republics of Kazakhstan and Uzbekistan.

What was once the fourth largest area of fresh water in the world has shrunk by two-thirds. It has fallen in depth by more that 14 metres (45 feet) in the past 30 years endangering the lives of the four million inhabitants of the region.

Soviet irrigation policies from the early 1960s diverted water from its two sources, the Amu Darya, or Oxus, and the Syr Darya in order to supply vast areas of cotton fields to the south of the Aral.

Infant mortality high

David Brundsen, professor of Geography at Kings College London, said the situation was far worse than they had anticipated.

What was once a thriving fishing industry has been destroyed and the climate has changed, with shorter dryer summers and longer colder winters.

Chemical pollution has caused serious illnesses.

Infant mortality is worse than any other developing country in the world, with 10% of children dying in their first year.

Death from chronic gastritis and kidney disease has increased by 15%, heart disease has doubled and incidences of kidney disease has risen 15-fold as drinking water becomes ever more salty and polluted.

Cancer has increased tenfold and death from TB is 21 times higher than it was in the 1960s.

Abandoned ships lie on the 80km (50 miles) of exposed seabed, now encrusted with salt and agricultural chemicals that are causing illnesses.

In the late 1980s the water level fell so low that the ancient sea split into two bodies of water.

Tony French, senior lecturer in geography at University College London, said that at this rate there would be very little left of the Aral Sea by the millennium.